http://antivirus.about.com/compute/antivirus/library/weekly/aa051601a.htm?te
rms=SULFNBK
Sulfnbk.exe
When hoaxes harm

Hoaxes. Many people believe them. Others aren't so sure but forward them
anyway "just in case". No matter how you slice them, hoaxes are a problem
and now they've taken a new tack. Originating in Brazil, a new hoax alleges
the file SULFNBK.EXE is in fact a virus and urges users to search their
system for the presence of the file. The hoax warns, even "Norton did not
discover it". Perhaps this is because the file is not infected.
A word of caution. Any executable file has the potential to be infected.
Worse, viruses like Magistr
(http://antivirus.about.com/library/virusinfo/blmagistr.htm) can pick
certain files at random, infect it, and send it off via email to others. So
the potential also exists for the file SULFNBK.EXE to be plucked by Magistr.
Of course, any portable executable (PE EXE) file up to 132K in length could
just as easily be sent, so there's no special distinction to the SULFNBK.EXE
file.
Just what is SULFNBK.EXE? It's a utility shipped as part of the Windows 98
operating system that allows users to restore long file names. Thus, anyone
using the Windows 98 operating system would find this file on their system.
If the hoax were received by these users, and believed, many might delete
the file thinking their antivirus software had somehow failed to detect the
virus. In fact, it wouldn't be the first time signature-based scanners
failed to detect a new virus, making the entire hoax even easier to believe.
If you aren't confused yet, you should be. Hoaxes survive simply by causing
confusion. They provide just enough real sounding information to guarantee a
pretty high degree of faith. The more believable, the more users willing to
pass it along. Hence hoaxes are very much like a manually driven virus,
relying on the user to deliberately pass along the "infection". In the case
of the SULFNBK.EXE warning there's a double whammy: as users pass it along,
it clogs email servers and drains resources; and those who delete it may
need the file at some point. Worse, this could be a stepping stone to a new
trend in hoax writing - targeting necessary system files, warning of dire
consequences and instructing users to immediately delete them. If the right
files were targeted, users following the warning's instructions could find
themselves worse off than if a "real" virus had hit. In other words, hoaxes
may soon be featuring malicious payloads deliberately executed by the
gullible and unsuspecting user.
Common sense provides the best cure. If you aren't sure, don't forward it.
Forget the "just in case" excuse - it's downright dangerous. Unless the
warning comes from a known and reputable source, send it to the Recycle Bin
and not to your friends and co-workers.